1. Field of the Invention
This invention relates generally to analyzing and reducing the effects of signal to signal cross-coupling, and more particularly, to reducing the noise problems induced by cross-talk by determining the worst case peak cross-talk noise experienced by a signal due to cross-coupling capacitances to other signals.
2. Description of the Related Art
In electronic circuit applications, such as sub-micron and PC-board circuits, signal to signal cross-talk is a problem that is very difficult to control and overcome. Often, a capacitance develops between two or more signals, called cross-capacitance. Due to cross-capacitance, transitions in one signal can influence the behavior of other signals. A signal whose behavior is influenced by the signal transitions of another signal, is called the victim signal. A signal that influences another signal by means of cross-talk is called the attacker signal. During different periods of the circuit operation, an individual signal can be a victim signal at one point in time and an attacker signal at another point in time.
Attacker signals can cause many problems such as: inadvertent transitions; transitions at wrong voltage levels; transitions too fast; transitions too slow; or noise problems included by signal to signal coupling capacitance, which can cause inadvertent state changes or erroneous satisfaction of logic conditions.
To date, the primary method of addressing cross talk problems has been essentially a trial and error approach. Currently, there are no automated methods to efficiently deal with the problems that are caused by cross-coupling signals. Generally, designers are reduced to predicting where cross-coupling may occur or only addressing the signals that are actually known to have cross-coupling tendencies, such as signal busses, which are generally known to have high coupling capacitance between adjacent bits, and very similar timing patterns.
The current methodology for analyzing signal cross-talk noise is to assume a lumped capacitance model, where all possible sources of cross-talk (attackers) switch at the same time with a specific worst case fast slope. A worst case peak cross-talk voltage on the victim node is calculated by summing the effects of all the individual attackers. Then, an attempt is made to prove that each coupling violation is false, which is an error-prone, time consuming, manual analysis. Furthermore, this process becomes more complex and inefficient as technology allows electronic circuits to become smaller and denser. The other approach to resolving problems under the lumped capacitance model involves simple attempts to eliminate cross-talk by changing the physical layout. This is also a highly inefficient procedure. The process of identifying and addressing the problems of cross-coupling induced signal noise with today's methods are, at best, guesswork, and they are inefficient.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.